Apparatus for delivery of printed sheets of paper or the like in successive stacks

Abstract

A delivery fan, comprising sets of blades at constant circumferential spacings, receives therebetween the sheets successively falling from an overhead infeed conveyor. The sheets fall off the delivery fan on hitting a set of abutment tines arranged interdigitatingly with the fan blades. A stack of sheets thus formed on a retractable platform is unloaded therefrom onto a delivery conveyor. A temporary sheet holder is provided which is angularly displaceable about the delivery fan axis between a working position, where it temporarily receive the sheets falling off the delivery fan pending unloading of the preformed stack of sheets, and a retracted position where the sheet holder allows the sheets to fall from the delivery fan onto the platform. The sheet holder is mounted to the shaft of the delivery fan via a pair of overrunning clutches and sprung from the retracted toward the working position. Consequently, when unlocked from its retracted position upon stacking of the sheets to a predetermined height on the platform, the sheet holder turns to the working position at the same angular velocity as the delivery fan.

What is claimed is:  
     
       1. An apparatus for delivery of sheets of paper or like material in successive stacks, comprising: 
       (a) infeed means for successively supplying sheets to be delivered;  
       (b) a delivery fan comprising a rotary shaft, and a plurality of sets of blades disposed at constant circumferential spacings on the shaft for receiving therebetween the successive sheets from the infeed means, the delivery fan being capable of rotation in a prescribed direction;  
       (c) abutment means to be hit by the successive sheets being carried by the delivery fan, the sheets on hitting the abutment means falling off the delivery fan with continued rotation thereof;  
       (d) delivery means underlying the delivery fan for receiving and having stacked thereon the sheets successively falling off the delivery fan;  
       (e) a temporary sheet holder angularly displaceable about the same axis as the delivery fan between a working position, where the temporary sheet holder temporarily receives the sheets falling off the delivery fan pending replacement of a preformed stack of sheets on the delivery means, and a retracted position where the temporary sheet holder allows the sheets to fall from the delivery fan onto the delivery means, the retracted position being spaced upstream from the working position with respect to the prescribed direction of rotation of the delivery fan;  
       (f) overrunning clutch means through which the temporary sheet holder is mounted to the shaft of the delivery fan for preventing the temporary sheet holder from rotating faster than the delivery fan shaft in a direction from the retracted to the working position, and for allowing the temporary sheet holder to rotate independently of the delivery fan shaft in a direction from the working to the retracted position;  
       (g) resilient means acting between the temporary sheet holder and a stationary part of the apparatus for biasing the former from the retracted toward the working position and hence for causing, in cooperation with the overrunning clutch means, the temporary sheet holder to travel at the same angular velocity as the delivery fan from the retracted to the working position; and  
       (h) drive means for moving the temporary sheet holder from the working to the retracted position against the bias of the resilient means.  
     
     
       2. The apparatus of  claim 1  wherein the temporary sheet holder comprises a pair of swing arms having a plurality of sheet holder prongs supported therebetween, and wherein the overrunning clutch means comprises: 
       (a) a pair of overrunning clutches; and  
       (b) a pair of carrier rings mounted to the shaft of the delivery fan via the respective overrunning clutches;  
       (c) the pair of swing arms of the temporary sheet holder being proximally secured to the respective carrier rings and supporting the sheet holder prongs between their distal ends.  
     
     
       3. The apparatus of  claim 1  wherein the drive means comprises: 
       (a) a pair of positioning rings rotatably mounted to the shaft of the delivery fan;  
       (b) a pair of stops formed one on each positioning ring for abutting engagement with the temporary sheet holder; and  
       (c) actuator means for bidirectionally rotating the pair of positioning rings relative to the delivery fan shaft between a first position, where the temporary sheet holder is held in the working position by being urged against the pair of stops by the resilient means, and a second position where the temporary sheet holder is held in the retracted position by being urged against the pair of stops by the resilient means.  
     
     
       4. The apparatus of  claim 1  wherein the temporary sheet holder has a plurality of air exit openings formed therein for emitting air under pressure in order to avoid interference with the sheets falling from the delivery fan when the temporary sheet holder travels from the retracted to the working position, and to allow the sheets to fall smoothly from the temporary sheet holder onto the delivery means when the temporary sheet holder travels from the working to the retracted position. 
     
     
       5. The apparatus of  claim 1  wherein the temporary sheet holder comprises a pair of swing arms with a plurality of sheet holder prongs supported therebetween, each sheet holder prong being hollow, defining a plenum chamber therein, and having a surface facing the delivery fan for receiving the sheets falling therefrom, and wherein a plurality of air exit openings are formed in said surface of each sheet holder prong. 
     
     
       6. The apparatus of  claim 5  wherein at least one other air exit opening is formed in another surface of each sheet holder prong which faces away from the delivery fan.